1. Field of the Invention
The present invention is in the field of mechanical projectors or archery equipment, and more specifically relates to a removable attachment for an archer's bow which permits the bow to be used for projecting balls, darts, or other missiles.
2. Description of the Prior Art
In U.S. Pat. No. 28,698, issued June 12, 1860 to Stevens, there is disclosed a cross-barrel in which a number of balls may be loaded from the breech end of the device and which are held in a firing position at the muzzle end of the device by spring clips. A rod, slidable in the barrel of the device, is attached at its rear end to the bowstring. When the bowstring is released, the rod attached to it bolts forward, and the front end of the rod strikes the ball held at the muzzle of the device knocking it forward toward the target. One can readily appreciate the tremendous impact which occurs when the rapidly moving rod strikes the stationary ball. The velocity difference is equal within a factor of 2 to the velocity with which the ball strikes the target. Such a high velocity impact could damage the ball, the rod, or both. To insure a large transfer of momentum to the ball, it is desirable that the rod be more massive than the ball. However, the more massive rod, which is attached to the bowstring, will tend to wrench the cross-bow from the user when the rod decelerates as it approaches its forwardmost position.
In U.S. Pat. No. 1,210,332, issued Dec. 26, 1916 to Kvistad, there is disclosed a mechanical leverage means for bending the bow, which has a guideway for directing dart-like arrows. The barrel is not tubular and it is not rigidly attached to the bow. In the Kvistad invention, the bowstring bears directly on the missile. This is a satisfactory arrangement where the rear end of the missile is flat and where the width of the rear end of the missle exceeds the possible lateral movement of the string. However, the Kvistad device is not suitable for projecting balls because the bowstring would tend to slide to one side or the other of the convex surface of the ball, thereby exerting an unpredictable lateral force on the ball which would seriously impair the accuracy of the device.
In U.S. Pat. No. 2,214,224, issued Sept. 10, 1940 to Douglas, there is disclosed a missile projecting device including a tubular structure. The device projects spherical missiles. The Douglas invention is really an air rifle in which the drawn bowstring, when released, drives a piston forward in a cylinder compressing the air therein. Some of the compressed air passes at a high velocity and pressure through an aperture, projecting the missile from the barrel. Immediately following the projection of the missile, and before the end of the stroke of the piston, a spike-shaped member enters the aperture blocking further passage of air therethrough and thus building up a back pressure to cushion the impact of the piston at the end of its stroke. As will be seen below, the Douglas invention is based on an entirely different principle from that of the present invention.
The present invention overcomes the impact which occurs in the Stevens cross-bow described above and the inability of the Kvistad device to project spherical missiles, also described above.